Why can't I add these expanded strokes to a single object?

[eobet]

add problem.afdesign

[GarryP]

I’ll assume that by “add these expanded strokes into a single object” you mean “with all of the child layers of the Layer layer selected, use the Geometry Add functionality to obtain a single Curves layer”.

You seem to have lots of little ‘strange’ shapes in that design which could be causing a problem, see attached image.
Tidying it up a little might help.

Note: Trying the Shapebuilder Tool on those selected layers gives a “Shapebuilder failed” message.

[eobet]

It's an imported object. I can't be manually tidying those things up. Affinity needs to have automated tools for this.

I just imported it into Illustrator instead and did expand, add, no issue. (Illustrator also has way better selection tools.)

[loukash]

4 hours ago, eobet said:

Illustrator also has way better selection tools.

Then simply use Illustrator. Problem solved.

[loukash]

4 hours ago, GarryP said:

Tidying it up a little might help.

I just checked the provided document, and while it's apparently not possible to boolean-add all objects in one step, it (almost) works when proceeding with just a subset of objects in multiple steps. It didn't take me longer than a minute to have all but one object merged.
Why the last object refuses to be merged, I don't know:

[firstdefence]

A bit of a butchers job

5 hours ago, eobet said:

It's an imported object. I can't be manually tidying those things up.

Imported from where?

Illustrator can combine this mess of expanded strokes in one click from the pathfinder panel Pathfinder: Shape Mode: Unite but you still have to manually edit the lines around the area's where the expanded strokes are badly aligned. So, as @loukash has noted use Illustrator because if you have a lot of these poorly drawn shapes you are in for an epic journey in Affinity.

add problem inc illustrator import.afdesign

[Alfred]

1 hour ago, firstdefence said:

butchers

*butcher’s

1 hour ago, firstdefence said:

area's

*areas

[firstdefence]

44 minutes ago, Alfred said:

*butcher’s

*areas

Cheers matey.

[v_kyr]

Another way is autotracing things into one curves layer.

[lacerto]

Obsolete.

[eobet]

Well, I took the result from Illustrator back into Designer and continued with the entire illustration, and then it came time to export it as an SVG/PDF the output was absolutely horrible.

Green result is Illustrator's export, and red result is from Affinity (both outside aligned strokes).

add problem.svg

[lacerto]

Obsolete.